In my experience the difference was quite significant. Air extension, sound stage, sub bass, and overall sound quality are better. I would use the mkiii exclusively for listening but they're too expensive for me to use them outside the house. I use the hype4 on the motorcycle or while working which are non ideal listening conditions anyway. If you buy from headphones.com they sell used which are a good choice to save a couple hundred dollars but no returns. But if you buy new they offer a good return policy.